Investigating Acid-Hydrolysis and Fermentation Method for Producing Ethanol from Nypa (Nypa fruticans Wurmb) Midrib

Abstract

Nypa (Nypa fruticans Wurmb) has high potential for producing ethanol because it has high cellulose and it is not used for food and feed.  This research was made to find: (1) suitable type and concentration of acid for hydrolyzing nypa midrib, (2) duration of hydrolysis to gain optimum yield of reducing sugar from nypa midrib, (3) suitable type and concentration of starter for fermenting process, and (4) duration of fermentation for optimally producing ethanol. Experiments consisted of hydrolysis and fermentation processes. Two factors were evaluated in hydrolysis process, i.e. type of acid (H₂SO₄ and HCl) by applying 3 concentration levels (1 M, 2 M, 3M) and duration of hydrolysis process (1 hour, 2 hours, 3 hours, 4, hours 5 hours).  The best result of hydrolysis experiments was then used in fermentation experiments.  The fermentation experiments involved two factors, i.e. type of starters (Saccharomyces cerevisiae and Zymomonas mobilis) with three levels of concentration (5 % (v/v), 7.5 % (v/v), 10 % (v/v)) and fermentation duration (2 days, 4 days, 6 days).  Result of the experiments indicated that use of HCl in hydrolysis was more effective for producing reducing sugar than that of H₂SO₄.  The best combination was application of 5 hours hydrolysis duration and use of 3M HCl whereas the yield of reducing sugar was 2.76% (28.86 mg/ml).  The 28.86 mg/ml of reducing sugar could be fermented to produce 4.00 mg/ml ethanol with alcohol content 3.80% by using 10% (v/v) Saccharomyces cerevisiae as starter in 6 days fermentation process.